Reactive oxygen species (ROS) can cause problems, e.g., in human health or in manufacturing processes. There are natural enzymes that promote the decomposition of ROS, e.g., superoxide dismutase, which catalyzes the conversion of superoxide (O₂⁻) radicals into molecular oxygen and hydrogen peroxide. However, such enzymes cannot be used under harsh conditions, e.g., in some manufacturing processes. Artificial antioxidant materials with a higher stability could solve this problem.

István Szilágyi, University of Szeged, Hungary, and colleagues have developed antioxidant nanocomposites that promote the decomposition of superoxide radicals. The composites are formed by the sequential adsorption of redox-active metal complexes and polyelectrolytes on nanoclay particles. The team started with layered double hydroxide (LDH) nanoclay particles, and then adsorbed the polyelectrolyte poly(styrene sulfonate), or PSS, onto the particles in a dispersion, followed by a copper(II) bipyridyl complex. Then, another polyelectrolyte was adsorbed, i.e., poly(diallyldimethyl ammonium), or PDADMAC, and finally, iron(III) citrate as a second metal complex. The adsorption of the different components to form the composite material is promoted by electrostatic interactions.

The resulting nanocomposite is highly selective for superoxide radical conversion. Its activity in other antioxidant tests was very low. The material could be used, e.g., to reduce oxidative stress in industrial manufacturing processes where natural enzymes cannot be used due to the temperatures or pH values involved.

• Catalytic antioxidant nanocomposites based on sequential adsorption of redox active metal complexes and polyelectrolytes on nanoclay particles,
  Zoltán Somosi, Nóra V. May, Dániel Sebők, István Pálinkó, István Szilágyi,
  Dalton Trans. 2021.
  https://doi.org/10.1039/d0dt04186f